1. FIELD OF THE INVENTION
The present invention relates to a flash device which is interchangeable with both an ordinary type photographing camera and an improved type photographing camera, and relates to the improved camera which is interchangeable with both an ordinary type flash device and the improved flash device.
2. DESCRIPTION OF THE PRIOR ART
Recently, a variety of flash devices and photographing cameras have been proposed in which various data transmissions are carried out between the photographing camera and the flash device.
Since the flash data and camera data have their own signal modes as well as differences in the number of signal series in accordance with the mechanism and the function thereof, a flash device which can be coupled to a camera may be limited. Namely, a flash device which may be coupled to a type of a camera or cameras of a certain camera maker, is inevitably limited as a so-called exclusive flash device.
The exclusive flash device of this type realizes various automatic operations required for flash photography. For example, when the flash device has been fully charged the camera is automatically switched to an operation mode for flash photography by providing a signal which indicates that the flash is ready, or flashing is suspended by inputting a quench signal when adequate exposure is obtained.
The flash device of this type is equipped with a microcomputer as a signal processing circuit of a flash data signal and a camera data signal. The microcomputer operates to output or input various data signals in accordance with programmed data and information.
The microcomputers usually provides the structure for feeding the power from a battery in the flash device, and generally uses a regulator for inputting a battery power voltage to apply an output voltage as a stabilized power source voltage.
Further, a flash device used with a camera having an automatic focusing capability, that is, a so-called auto-focus camera, is provided with an auxiliary light source for lighting an object to be photographed in conjunction with focusing of the camera.
The lighting by the auxiliary light source is necessary for obtaining a bright object through a view finder for flash photography and for obtaining a projected image of the object as the object for the focusing in the case where the object is flat or is low in contrast.
An infrared light emitting diode or filament lamp may be used as the auxiliary light source. When such a filament lamp is used, a red color filter is provided at the front face thereof in order to project red color light to the object.
With such a conventional flash device described above, the battery for the flash device serves as a power source for lighting the auxiliary light source. Therefore, the flash device is disadvantageous in that, if it is caused to light during the charging operation, an amount of light projected is lowered resulting in insufficient lighting effect.
In more detail, since a booster circuit consumes a comparatively large amount of electrical power until the level, the voltage, level of the battery drops considerably. Under this condition, if the auxiliary light source is energized during such a charging period, sufficient amount of light cannot be obtained by the auxiliary light source.
The above problem accompanying the conventional flash device using an LED may be significant in a flash device using a filament lamp as an auxiliary light source.
Moreover, when the power supply is simultaneously carried to both the booster circuit and the auxiliary light source, the reduction in the voltage level of the power source is more significant. As a result, it is somewhat difficult to supply constant power to circuit elements such as a micro-computer which are to be driven by the constant voltage source,
The conventional flash device and the conventional photographing camera ar disadvantageous in that the flash device and the photographing camera have no compatibility with respect to each other because the combination of the flash device and the camera- which can load the flash device is restricted.
Therefore, upon developement of a new type of camera an exclusive flash device which can be loaded on that camera has to also be developed. In other words, an exclusive flash device must be newly developed for every camera developed.
The exclusive flash device thus developed in line with development of the camera is a very convenient flash device having various automatic functions but the provision of the exclusive flash device results in that, in the case where a user buys an improved type camera it is also necessary for the user to buy such an exclusive flash device to the improved camera. Further, the cost of the exclusive flash device may be relatively high because it must be newly developed.
Furthermore, the conventional flash device is required to deal with various flash data signals and camera data signal.
In a clip-on type flash device, the above various data transmission is carried out between terminals provided to a fitting leg of the flash device and a hot shoe terminal of a camera. On the other hand, in a grip type flash device, the data signal transmission is carried out by connecting a connecting cord to the camera. However, the data transmission by terminals or the connecting cord encounters difficulty such that mechanisms and functions of the flash device and the camera become complicated day after day, as aresult of which the number of signals to be transmitted is increased.
Since several terminals for the above data signal transmission are provided in a narrow space with electrical insulation, increase in the number of terminals is restricted. Accordingly, a plurality of data signals are transmitted through a single terminal. However, the data signals have different transmitting directions between the flash device and the camera and also have different transmission sequences. Therefore, this results in increasing complexity of the transmission circuit structure as the number of data signals increases.
In order to increase an amount of flash light, it has been proposed that a plurality of the flash devices be used simultaneously. In this case, the corresonding connecting terminals of the respective flash devices are used in common and they are then electrically connected with the corresponding terminals of the camera. Therefore, it is necessary to improve a data output circuit of the flash device to accomplish such complicated data communication.
For instance, assuming that one flash device is sufficiently charged and becomes ready for flashing but the other flash device is under charging and has not yet reached flashable condition, a signal indicating the flash-ready condition, which is produced by the one flash device, may flow into the other flash device. As a result, undesired electrical power consumption may occur or erroneous operation may occur. Moreover a problem which causes breakdown of circuit elements may occur.
Such problems occur easily as the number of flash devices to be used for increasing the amount of flash light increase and further the influence thereof becomes more distinctive.
The battery contained in the flash device consumes its power resulting in an occurrence of voltage drop as the number of times of flashing increases and a leakage current increases during a storage period. Further, when an operation of a booster circuit starts. a battery voltage decreases due to power consumption of such a booster circuit. The degree of voltage drop of the battery differs depending on consumption of the power.
Therefore, a conventional flash device is provided with a regulation circuit to adjust the output voltage of the battery to a constant stabilized voltage. However, with such regulation, it may be somewhat difficult to obtain a stabilized voltage with high accuracy. Thus, the regulator circuit is not suitable for a power source having high accurancy for supplying power to a microcomputer and circuits which require an accurate reference voltage.